This project is an attempt to elucidate the biochemical mechanisms responsible for morphological differentiation in the fungus, Mucor rouxii. Our study is focused on the cell wall. We would like to learn how the fungus elaborates the different types of cell walls that characterize each step of its life cycle; what enzymes are involved in wall formation; how these polymers are synthesized and assembled into cell walls with various characteristic shapes; what biochemical controls regulate the formation and spatial deposition of wall constituents; what cytoplasmic structures participate in the process of wall formation. We are using the process of chitin biosynthesis as a model system for these studies. Our broad plans encompass the study of the entire asexual life cycle of this fungus. We are particularly interested in the phenomenon of mycelial-yeast dimorphism and that has led us to concentrate our interests on hyphal development. Elucidation of the mechanisms of hyphal morphogenesis appears to be a key to understanding not only the most common mode of growth of fungi, but also other mode of cell morphogenesis (yeast growth, conidiation) which may be regarded as variations of the central mechanism of hyphal morphogenesis. One additional objective of this study is to increase our understanding of the mode or lack of action of polyoxins (new antifungal antibiotics).